Piston structure



June 20, 1944. v VAN DEN BERG 2,352,041

PISTON STRUCTURE Filed July 23, 1940 7 GAS CAB/.5 LIQUID Inventor:Walter" van den Berg, by 7 5 His Attorney Patented June 20, 19442,352,041 PISTON-STRUCTURE Walter van den Berg, Cologne-Mulhelm, Ger-Alien Property Custodian many; vested in the Application July 23, 1940,Serial In Germany January 31, 1940.

Claims.

In fluid filled electric cable installations, as the cable heats andcools with changes of load thereon, expansion and contraction of theimpregnating medium-takes place. To avoid undue changes of pressurewithin the conductor enclosure, means are provided to receive the fluidmedium from the cable as it expands and to feed it back to the cable asits temperature and that of the cable decreases. To accomplish this,variable capacity reservoirs are employed in which a gas under pressureis employed as a yieldable means to accommodate any increasein volume ofthe impregnating magages the under surface of the cover 3, the latterbeing clamped in place by an annular series of clamping bolts l3 whichenter the ring. Gas under Positive predetermined pressure is admitted tothe'plston chamber 1 by suitable means, such as the pipe it, having anyusual form of shutoff means. The bottom wall 2 of the tank has a pistonstop l5 of suitable construction, in this case a ring which is brazed orwelded to the wall.

terial and to feed it back to the conductor enclosure as it contracts.Care must be exercised to prevent the gas from mixing with theimpregnating material. iAS ordinarily constructed, these reservoirs areexpensive and require the utmost care in their manufacture, and usuallya considerable amount of special manufacturing apparatus.

The object of my invention is the provision of an improved pistonstructure for cylindrical reservoirs which is simple in construction,reliable in operation, and of relatively low initial cost.

For a consideration of what I believe to be novel and my invention,attention is directed to the accompanying description and the claimsappended thereto.

In the attached drawing, which is illustrative of my invention, is showna reservoir in vertical section.

The reservoir comprises a tank having a cylindrlcal wall I of relativelythin metal, a bottom wall 2 which is curved inwardly to give it thenecessary strength to resist internal pressure which is above that ofthe atmosphere, and a cover 3. Inside of the casing so formed is a ring4 which is brazed or otherwise secured thereto in a manner to provide afiuidtight joint. Inside of the casing is a cylinder 5 of heavier metalwhich has a carefully smoothed inner surface as it is on that surfacethat the free piston 6 moves up and down. It is important to make theinner surface smooth for upon it in large measure depends the separationof the gas in the chamber 1 above the piston and the liquid or otherfluid from the cable in the chamber 8 below the piston. This chamber isin free communication with the tank chamber 9, as for example throughlateral openings l0,.the effect of which is to greatly enlarge thecubical contents of the retaining or storage space for cable liquid. Theupper end of the cylinder is supported by the ring 4 and the two partsare united by a brazed or welded joint II. The upper end of the cylinderand the inner part of the top surface of the ring are chamfered toreceive a compressible packing l2 which ennumber of floating rings ingrings Liquid or other fluid from the cable is admitted to the chambers 8and 9 through the pipe IS. The stop prevents the piston when in itslowermost position from interfering with the admission of fluid to thechamber 8 from the cable.

The free piston 6 comprises top and bottom plates l1 and i8 betweenwhich are located a l9, two being shown in the present illustration.Each ring has a pair of oppositely inclined or beveled peripheralsurfaces 20 for engagement with packing rings 2| which are made ofmaterial that is somewhat elastic. The top and bottom plates or headsare also provided with beveled faces or surfaces 22 which cooperate withthe surfaces 20 to force the packing rings outwardly into contact withthe wall of cylinder 5. The floating rings and the end plates havecooperating engaging shoulders 23 and 24 which prevent undue lateraldisplacement of one part with respect to another, especially whenpressure is applied to the plates. Each floating ring has shoulders onopposite sides thereof, one shoulder suchas 24 engages a flange on ahead while shoulder 25 engages a shoulder on the adjacent ring. Thepacking rings are of trapezoidal cross-section, are fitted intosubstantially conical recesses, and are pressed tightly against the wallof the cylinder by a wedging action due to the beveled or conedsurfaces, for example when the upper plate I! is subjected to gaspressure and the lower plate I 8 to cable liquid pressure. The packingrings may be made of rubber where the fluids to which they are exposeddo not adversely affect them, or they may be made of any otherconvenient artificial material which is resistive to the action offluids.

The plates are loosely connected which permits of a limited freedom ofmovement of the floati9. This has the advantage of equalizing thepressures on the packing rings instead of causing a higher pressure atone region over that of another. To accomplish this, the upper plate I!has a hub-like socketed center which is screw threaded to receive andretain the threaded part of member 26. The member has a sleeve-likeextension in which is located a cylindrical element 21 secured to thelower head l8, the two parts 26, 21 having an easy sliding flt, thusacting to allgnthe heads. The sleeve 28 has a slot 28 to receive an endof a pin 28 fastened to the element 21, the slot walls and the pinlimiting the maximum separation of the end plates and preventingrelative angular movement of the parts. The lower plate has a hub-likesocketed center portion which has a screw threaded opening to receivethe lower end of the cylindrical part 21. The screw threaded arrangementpermits of a limited amount of vertical adjustment. As indicated, thearrangement above described permits of limited independent movements ofthe heads and rings. Because the heads and floating rings are notpositively connected, the pressures on the several packing rings areequalized both vertically and laterally with the result of affording acomplete separation of the gas and cable liquid. Stated another way, thefloating rings have a limited amount of play. The top and bottom plateshave smooth edges and make an easy fltwithin the cylinder so that, theywill not injure the smooth surface of the cylinder wall as the pistonmoves up and down. As will be noted, the end plates are always underpressure when the reservoir is in use, the pressures acting in oppositedirections. As the cable liquid or fluid expands, the free piston ispushed upwardly in opposition to the gas pressure in chamber 1. When thecable fluid contracts, the gas pressure forces the piston downward andthus the cable fluid is maintained under the predetermined positivepressure and the formation of voids or gas containing spaces in thecable prevented. I have described the chamber 1 fllled with gas andchambers and 9 with cable fluid but this arrangement can be reversed.The free piston being constantly under opposing fluid pressures, thepacking will always be under pressure and in contact with the cylinderwall. As a result of this, there will be at'all times a completeseparation of the fluids and there will be no opportunity for one fluidto leak into the other. There will be very little tendency in thisrespect for the pressures quickly become equal and opposite.

From another viewpoint, a piston structure according to my invention hastwo axially spaced end plates l1, I! with annular cylindricalprojections facing each other and forming cylindrical surfaces orshoulders 23. The two end plates or heads are connected by a looseconnection 21,

28, 29 permitting limited axial movement of each head independent of theother head. Ring means are interposed between the heads. These rin meanshave an outer diameter equal to that of the heads and form cylindricalprojections telescoping with the'p'rojecti'ons of the heads and formingtogether with the latter annular grooves for receiving elastic packingrings.

My invention has been described in connection with a cable but it may beused with other types of electrical apparatus where separation of twofluids, both under pressure, is desirable.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A piston for use in a cylinder the opposite ends of which aresubjected to fluid pressures comprising a member in the cylinderseparating the two fluid pressures and movable in response to changes ofpressure on opposite sides thereof, the member having end heads, each ofwhich has an outwardly beveled surface, means connecting the headspermitting of a limited axial movement of one with respect to the other,floating rings located between the heads and capable of limited axialmovements with respect to the heads, the ringshaving outwardly beveledsurfaces, and packings between the beveled surfaces of the rings andbetween a ring and a head, said packings being forced outwardlyagainst'the cylinder wall by the opposing fluid pressures on said endheads.

2. A piston for use in a cylinder the opposite ends of which aresubjected to fluids under predetermined positive pressure, comprising amember having end heads, an annular flange on each head, a mechanicalconnection between the heads permitting a limited amount of independentaxial movement thereof, a series of floating rings ach having annularshoulders on opposite sides thereof, certain of said shoulderscooperating with each other and others with the flanges on the heads torestrict sidewise movement while permitting of a greater axial movement,and compressible packings adjacent the shoulders which are forcedoutwardly by the pressures at opposite ends of the cylinder exerted onthe heads.

3. A piston for use in a cylinder the opposite ends of which aresubjected to fluids under predetermined-positive pressure, comprising amember having end heads, each of which has a conical peripheral surface,an annular flange on each head, a series of floating rings, each havingoutwardly extending conical surfaces and annular shoulders, one on eachside thereof, one of the shoulders on each of the end rings engaging aflange on a head, the adjacent shoulders on the rings engaging eachother, the shoulders and flanges permitting axial movement of one partwith respect to another, packings located between the conical surfaceswhich are forced outwardly against the cylinder wall due to the opposingpressures at opposite ends of the cylinder exerted on the heads, andmeans for limiting the separation of the end heads.

4. Piston structure comprising axially spaced end heads of like diameterwith annular projections facing each other, loose connecting meansaligning the heads and permitting limited independent axial movement ofeach head, floating ring means having an outer diameter equal to thediameter of the heads being interposed between the heads and havingannular projections telescoping the head projections and definingtherewith annular grooves for accommodating packing ring means.

5. Piston structure comprising axially spaced heads of like diameterhaving annular projections facing each other, means loosely connectingtheheads and permiting limited independent movement of each head, aplurality of floating rings each having a diameter equal to that of theheads and forming an annular axial projection on each side, the annularprojections of adjacent rings telescoping each other and forming agroove for accommodating a packing and the ring projections adjacent theheads telescoping the respective projections of the heads and formingother annular grooves for accommodating packing rings.

' WALTER van m BERG.

